Mumbai witnessed most polluted winter in four years: CSE report
According to the report titled ‘Winter pollution in megacities: The growing crisis outside Delhi’, Mumbai’s most polluted air day was on January 18, when PM2.5 levels peaked at 148µg/m³
The concentration of PM2.5— fine, inhalable particulate matter with less than 2.5 micrometres in diameter— in Mumbai this past winter was at its highest in four years, according a report shared by the Centre for Science and Environment (CSE).
High-level content of PM2.5 causes air pollution which can affect people’s health.
As per the analysis of Central Pollution Control Board (CPCB) data by the Delhi-based CSE, published this week, from an average of 64ug/m3 (micrograms per cubic metre of air) in the winter of 2019-20, PM2.5 levels in Mumbai rose to 77µg/m³ in 2022-23, worsened by 14%.
According to the report titled ‘Winter pollution in megacities: The growing crisis outside Delhi’, Mumbai’s most polluted air day was on January 18, when PM2.5 levels peaked at 148µg/m³.
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On the whole, January was the most polluted month of the winter in season, with PM2.5 averaging out at 95µg/m³, it added.
According to the report, Mumbai’s Bandra-Kurla-Comlpex or BKC was found to be the most polluted location this past winter, with an average PM2.5 measure of 122µg/m³, which is double the 24-hour standard of 60µg/m³ according to the national ambient air quality standards (NAAQS). The annual standard is 40ug/m3.
In addition to BKC, these include Deonar (121µg/m³), Mazagaon (109µg/m³), Navy Nagar (107µg/m³) and Chakala (97µg/m³). The analysis also finds that Mumbai had the least number of “good” AQI days among the megacities whose data was studied by CSE (excluding Delhi).
In contrast to the increasingly popular notion that Mumbai has overtaken Delhi as India’s most polluted city (with respect to suspended particulate matter pollution), CSE’s report shows that the National Capital remains in the top spot, with a citywide winter average of PM2.5 measure of 151µg/m³ in 2022-23. Next is Kolkata (80µg/m³), followed closely by Mumbai’s 77µg/m³, as mentioned earlier.
Though third in rank, researchers at CSE noted a worrying trend in Mumbai’s data. “Keeping Delhi aside, because PM pollution is exceptionally higher there, we analysed data from 66 monitors across Mumbai, Howrah-Kolkata, Bengaluru, Hyderabad and Chennai. Of these, the five most polluted areas were all from Mumbai,” said Avikal Somvanshi, programme lead (urban lab), CSE, and the report’s lead author.
“This winter, several mega cities (excluding Delhi) have recorded higher seasonal PM2.5 averages compared to their previous winter. This clearly indicates that the overall emissions are high or may be rising in those cities,” states the report.
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Explaining possible reasons for the sudden spike in pollution this past winter, Gufran Beig, founder-director of SAFAR and a scientist with the National Institute of Advanced Studies (NIAS), said, “La Nina conditions, referring to cold ocean temperatures in the Equatorial Pacific, prevailed for the third consecutive year this winter and are expected to become more prominent in the near future due to climate change. This led to extremely calm winds around the Mumbai metropolitan region and negligible dispersal of pollutants.”
“It’s also likely that Mumbai’s emissions at source, including construction work and vehicles, are intensifying. But meteorology is playing a big role too. In winter, Mumbai used to see a reversal of wind directions at least every three to four days, but over the past few years, this happens only once every 15 days or so. This affects the ability of the city to clean its air,” he said
“And because winds have been blowing predominantly from North India, the import of transboundary dust from more polluted regions could also be exacerbating the local situation,” Beig added.